Justification:
There are no published data about population trends or total numbers of mature animals for this species. There is very little available information about its extent of occurrence or its area of occupancy. There have been no quantitative analyses examining the probability of extinction of this species. As a result, we have insufficient data to properly assess the species against any of the IUCN criteria, and propose a listing of data deficient (DD).

Hippocampus zosterae previously was listed in 1996 as VU A2cd under the 1994 criteria. This assessment was based on suspected past declines in occupancy, occurrence and habitat, as well as on potential levels of exploitation. In reassessing the species under the new criteria and with greater taxonomic understanding we find that no appropriate data on biology and ecology, habitat, abundance or distribution are available for this species. Further research is needed, so we recommend the species be listed as DD under the new criteria.

This species is found in shallow seagrass flats, especially in association with Zostera and other seagrass, and is found in floating vegetation (Lourie et al. 1999).

This species may be particularly susceptible to decline. The information on habitat suggests they inhabit shallow seagrass beds (Lourie et al. 1999) that are susceptible to human degradation, as well as making them susceptible to being caught as bycatch. All seahorse species have vital parental care, and many species studied to date have high site fidelity (Perante et al. 2002, Vincent et al., in review), highly structured social behaviour (Vincent and Sadler 1995), and relatively sparse distributions (Lourie et al. 1999). The importance of life history parameters in determining response to exploitation has been demonstrated for a number of species (Jennings et al. 1998).

Hippocampus zosterae are one of the more popular seahorses in the aquarium trade (Vincent 1996, Wood 2001). Florida has a small directed trawl fishery in shallow grass beds off the west coast for H. zosterae where they are landed in a live bait trawl fishery. In this fishery alone, tens of thousands of H. zosterae are collected each year for the aquarium trade (Vincent and Perry, in prep.). Hippocampus zosterae occupies the 2nd rank of the top 10 fishes exported from Florida for the aquarium trade (Wood 2001).

The American Fisheries Society (AFS) lists the United States populations of H. zosterae as Threatened due to habitat degradation (Musick et al. 2000). While this status may apply on a national level, we did not find information that would justify such a listing for the species as a whole.

The entire genus Hippocampus was listed in Appendix II of CITES in November 2002. Implementation of this listing will begin May 2004. Full monitoring of the trade is underway in the United States, however this is dependent on traders’ declarations. Seahorses are listed under Title 68 (Rules of the Fish and Wildlife Conservation Commission) of the Florida Administrative Codes. The targeted fishery for the aquarium trade in Florida is monitored and regulations are in place, such as a limitation on the number of commercial harvesters, however the non-selective exploitation is not monitored in any state. The take of seahorses for the aquarium trade is prohibited in the USVI and Puerto Rico. Stock assessments are needed in order to evaluate the sustainability of the fishery and establish appropriate management guidelines. Further research on this species biology, ecology, habitat, abundance and distribution is needed.